1. Field of the Invention
This invention relates generally to backflow check valves for use with liquid flow and administration structures for medical purposes.
2. Description of the Prior Art
A common problem of known devices of the conventional type is that upon reversal of liquid flow through tubing from a hypodermic syringe or the like, the known type check valves fail to respond as quickly as desired to the closed position. That it, there is always the risk of backflow from the output to the input, which in many instances if very undesirable, and in some cases, even deadly.
There have been devices made to be normally closed and under stress, whereby the valve in order to remain open must be subject to a high flow pressure, and thus when the flow pressure is decreased, the valve will quickly close. This is a great improvement over the afore-mentioned check valve; however, it still can be improved upon. The disadvantage of this type is that the valve disc itself may tend to move off center and thus have a tendency to bind an edge against one of the peripheries of the enclosing wall.
Existing prior art patents which may be pertinent to the present invention are as follows:
U.S. Pat. No. 4,369,812--1/25/83--Paradis et al. PA1 U.S. Pat. No. 4,310,017--1/12/82--Raines PA1 U.S. Pat. No. 4,286,628--9/1/81--Paradis et al. PA1 U.S. Pat. No. 4,246,932--1/27/81--Raines PA1 U.S. Pat. No. 4,222,407--9/16/80--Ruschke et al.
U.S. Pat. Nos. 4,246,932 and 4,310,017 were both invented by the same inventor as the present one, and both are assigned to the same assignee as the present application. The first patent discloses a flexible disc 150 which rests on a plurality of ribs 166 located about the lower surface of the disc. Disc 150, which is normally closed, folds open under high pressure, and thus permits flow of the desired liquid. However, upon reversal of flow, the disc will promptly close and prevent same. A triangular support 186 holds the mid-portion of the disc against the cross bar 170 (see FIGS. 2, 4 and 5). However, except for the pressure between the point of the triangular support and the bearing surface of the cross bar on opposite sides of the flexible disc 150, there is nothing present to assure that the disc does not move sideways.
The other U.S. Pat. No., 4,310,017, discloses male and female hubs which are sonically welded together with a flow control disc 50 therebetween. However, this device has some of the limitations already stated above.
U.S. Pat. No. 4,222,407 discloses a flexible disc 68 which rests upon a rib 58 which extends entirely across the diameter of the disc. This rib normally holds the disc against the valve seat (surface 20) to thus be normally closed. However, upon pressure flow of fluid, the disc will fold over rib 58 and permit liquid passage thereby. Again, this device does not provide any specific structure for preventing the disc from sideways movement and thus binding of a peripheral edge against an inner sidewall of the chamber of the assembled body.
Both U.S. Pat. Nos. 4,286,628 and 4,369,812 are to Paradis et al., and disclose other check valve structure involving movable discs therewith. A two-part body is assembled to contain a flexible control disc therebetween. Longitudinal channels 26 are provided at the periphery of control channel 21 to facilitate reverse flow through the valve. However, structure like that disclosed in the present invention for preventing binding or off center movement of the valve disc is not disclosed.
None of the known prior art devices offer the new and novel features of the present invention.